To address the needs for increasing efficiency in power conversion, stratified structures like thermal barrier coatings, are used to increase operation temperature. Also advanced material processing like 3D laser printing of metals and ceramics are based on a layer-to-layer process at high temperatures, resulting in non-homogeneous components. Both systems require more and more detailed investigation methods to characterise the material properties of the resulting structures and to optimize the relevant processes. To address the required needs in advanced material characterisation recently an attempt was started to develop a unique measurement set-up for advanced material characterisation. This method is based on the well know laser flash principle, which was improved by adding supplementary heating sources and additional detection channels. Combining different heating mechanism and heating times with the two-dimensional measuring of the thermal flow across the sample enables the determination of different opto-thermal parameters and other material properties, e.g. mechanical contact, electrical conductivity or optical data, which also depend on or affect the flow of heat. In this paper we describe the implementation of the different optical methods to measure the thermal heat flow by point-like and two-dimensional temperature measurement and present first results on several samples.
Zusammenfassung
Das Ziel dieser Arbeit bestand in der Entwicklung eines langwelligen
Strahlungsthermometers zur berührungslosen Messung von
Oberflächentemperaturen in stationären Gasturbinen während
des Betriebs der Turbinen innerhalb des EU-geförderten Projektes
„Sensors Towards Advanced Monitoring and Control of Gas Turbine
Engines (Acronym STARGATE)“. Im Rahmen der Arbeit wurden die
infrarot-optischen Eigenschaften der Wärmedämmschichten und
der vorhandenen Brenngase am ZAE Bayern bei hohen Temperaturen bis
1600 K und Drücken bis 13 bar bestimmt. Mit Hilfe
dieser experimentellen Charakterisierungen konnte ein geeigneter
Spektralbereich um 10 μm für das langwellige
Strahlungsthermometer identifiziert werden. Entsprechend dieser
Erkenntnisse wurde zunächst ein Laboraufbau mit geeigneten
optischen Bauteilen (Filter, IR-Wellenleiter, etc.) realisiert und
verifiziert. Anschließend wurde ein Prototyp für Messungen in
Gasturbinen während des Betriebs der Turbinen entwickelt und in
einem Turbinenteststand der Firma Siemens AG in Berlin erfolgreich
getestet. Abschließend wurde eine Unsicherheitsanalyse
durchgeführt, die eine erweiterte Messunsicherheit der gemessenen
Temperaturen von etwa ± 30 K ergab.
Stationary gas turbines are still an important part of today’s power supply. With increasing temperature of the hot combustion gas inside a gas turbine, the efficiency factor of the turbine increases. For this reason, it is intended to operate turbines at the highest possible gas temperature. Therefore, in the combustion chamber and especially at the position of the first stage guide vanes the gas temperature needs to be measured reliably.
To determine the gas temperature, one promising approach is the application of a non-contact measurement method using a radiation thermometer. A radiation thermometer can measure the gas temperature remotely from outside of the harsh environment.
At ZAE Bayern, a high temperature and high-pressure gas cell has been developed for this purpose in order to investigate gases and gas mixtures under defined conditions at high pressures and high temperatures. This gas cell can be placed in a FTIR-spectrometer in order to characterize the infrared-optical properties of the gases.
In this work the measurement setup is introduced and gas mixtures, which are relevant for gas turbine applications are analyzed thoroughly. The derived results are presented and discussed in detail. To identify suitable wavelength regions for non-contact gas temperature measurements, first tests have been performed. Based on these tests, an appropriate wavelength region could be chosen, where future gas temperature measurements can be carried out.
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